Electromicrometer

ABSTRACT

A PIEZOELECTRIC CRYSTAL IS ARRANGED BETWEEN THE MOUNTING SLEEVE OF A STANDARD MICORMETER AND AN AUXILIARY MOUNTING SLEEVE FIXED TO A MOUNTING STRUCTURE AND THE DIMENSION OF THE PIEZOELECTRIC MEMBER IS VARIABLE IN THE DIRECTION OF RELATIVE OF THE MICROMETER SPINDLE SO   THAT A VOLTAGE APPLIED TO THE PIEZOELECTRIC MEMBER CHANGES THE DISTANCE BETWEEN THE MOUNTING STRUCURE AND THE MICROMETER SLEEVE FOR FINE ADJACENT OF THE MICROMETER.

Oct. 12, 1971 A, M. SMITH 3,611,571

' ELECTROMICROMETER j, Filed Jan. 29, 1970 F I6. I

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I6 I VOLTAGE SOURCE 2! 23 22 II I w! w M" 4.... 4 I. -1 l Q i .h I 39 FIG 2 VOLTAGE 28 SOURCE VOLTAGE SOURCE mvisN'mR,

ABBOTT M. SMITH ATTORNEYS United States Patent 3,611,577 ELECTROMICROMETER Abbott M. Smith, Webster, N.Y., assignor to Tropel, Inc., Fairport, N.Y. Filed Jan. 29, 1970, Ser. No. 6,894 Int. Cl. G01b /00 US. Cl. 33166 18 Claims ABSTRACT OF THE DISCLOSURE A piezoelectric crystal is arranged between the mounting sleeve of a standard micrometer and an auxiliary mounting sleeve fixed 'to a mounting structure, and the dimension of the piezoelectric member is variable in the direction of relative motion of the micrometer spindle so that a voltage applied to the piezoelectric member changes the distance between the mounting structure and the micrometer sleeve for fine adjustment of the micrometer.

THE INVENTIVE IMPROVEMENT Mechanical micrometers adjustable to .0001 inch are generally known and are suitable for manual use. However, in some circumstances, and particularly in optical equipment, such micrometers are clamped in place in a mounting structure, and even finer adjustments are desirable. The invention recognizes the possibility of achieving such finer adjustments with a piezoelectric member arranged in series with the micrometer, and the invention aims to accomplish this with a simple and convenient adaptation of conventional micrometers so they are interchangeable with standard micrometers.

SUMMARY OF THE INVENTION A conventional micrometer has a mounting sleeve and a movable spindle, and the invention adds a member fixed to a mounting structure and a piezoelectric member having one region engaging the fixed member and another region secured in place relative to the micrometer sleeve. The dimension of the piezoelectric member between such regions is variable in the direction of relative motion of the spindle, and a voltage is applied to the piezoelectric member for varying this dimension to adjust the distance between the micrometer sleeve and the mounting structure for fine adjustment of the micrometer.

Drawings:

FIGS. 1 and 2 show partially schematic, elevational views of alternative embodiments of the inventive electro micrometer; and

FIG. 3 is a partially schematic, partially sectioned, elevational view of another preferred embodiment of the inventive electro micrometer.

DETAILED DESCRIPTION Conventional micrometers as best shown in FIG. 1, include a mounting sleeve 12 and a thimble or body that is mechanically adjustable to position movable spindle 11. Sleeve 12 can be clamped in a C-shaped frame such as illustrated in FIG. 2 to form a caliper micrometer, or can be clamped in other mounting structures where movement of spindle 11 would be useful. Such structures include equipment such as optical devices where movement of spindle 11 positions mirrors, lenses, or other elements. The inventive electro micrometer has a finer adjustment capacity than can be sensed in manual operation, but is useful for precision adjustment from a mounting structure.

As schematically arranged in FIG. 1, clamping sleeve 12 of a micrometer is clamped in arm 13, and a piezoelectric member 14 is secured between arm 13 and mounting bracket 15 which is fastened to a mounting structure 17 by screw 16. A voltage source 18 applies voltages to piezoelectric member 14 to change its dimension in the direction of movement of spindle 11 so that the distance between mounting structure 17 and micrometer sleeve 12 is adjustable with the applied voltage for fine adjustment of the micrometer. Coarse adjustment is obtained in the usual way by turning thimble 10.

FIG. 2 shows a caliper micrometer schematically arranged according to the invention. Arm 21 of C-frame 20 is clamped to the mounting sleeve of the micrometer so that thimble 10 can be turned to position spindle 11. The arm 23 of frame 20 carrying anvil 22 is secured to the mounting structure 39, and piezoelectric member 19 is secured between arms 21 and 23 in frame 20. Voltage from source 24 adjusts the dimension of piezoelectric member 19 in the direction of movement of spindle 11 for fine adjustment of the micrometer.

FIG. 3 shows an alternative preferred embodiment of the inventive electro micrometer using a conventional micrometer having a mounting sleeve 12, a thimble 10, and a movable spindle 11. A housing 25 is secured to micrometer mounting sleeve 12 to surround sleeve 12 and spindle 11, and an auxiliary clamping sleeve 26 is clamped and fixed in place in mounting structure 28. A surface 29 of fixed member 26 extends inside surface 30 of housing 25, and surfaces 29 and 30 mutually engage and are relatively movable a small distance. An O-ring 31 in housing 25 is arranged adjacent surface 30 to engage surface 29 to provide a seal and allow relative movement. Another O-ring 27 is arranged inside clamping sleeve 26 to engage spindle 11 for a sealed and relatively movable fit.

A piezoelectric member 32 of generally tubular form is arranged inside housing 25 to surround sleeve 12 and spindle 11 and be coaxial with housing 25 and fixed member 32 butt against surfaces of fixed member 26 and housmember 26 and the inside of piezoelectric member 32 for fitting and centering. The axial ends of piezoelectric member 22 butt against surfaces of fixed member 26 and housing 25 as illustrated. Housing 25 and fixed member 26 are thus separated by the axial length of piezoelectric member 32.

A resilient ground conductor 40 is arranged around sleeve 12 to engage the inside surface of piezoelectric element 32 to ground such surface through sleeve 12, sleeve 26, mounting structure 28, housing 25, and the grounded portion of a jack 35. Jack 35 in housing 25 leads in an insulated conductor 36 from voltage source 37 which is applied through lead 38 to the outside surface of piezoelectric element 32. Piezoelectric element 32 is made so that its longitudinal or axial dimension in the direction of relative movement of spindle 11 is variable with the voltage applied from source 37. A change in the axial dimension of piezoelectric member 32 as a function of the applied voltage changes the distance between micrometer sleeve 12 and mounting structure 28 for fine adjustment of the micrometer.

The fixed member clamping sleeve 26 is preferably the same diameter and size as a conventional micrometer mounting sleeve 12 so that the resulting electro micrometer can be substituted for standard micrometers in existing equipment. The only dimensional differences in the inventive electro micrometer compared to conventional micrometers is a slight increase in overall length and maximum diameter necessitated by housing 25.

In operation, the inventive electro micrometer is secured to a mounting structure 17, 28 or 39, and thimble 11 is adjusted manually for coarse positioning of spindle 11 to within .0001 inch of the desired position relative to such mounting structure. Then various voltages from respective source 18, 26 or 37 are applied for fine adjustment of the electro micrometer with the resolution of spindle 11 relative to the mounting structure being to a precision as fine as 40 angstrom units. This allows utra fine adjustment of whatever measurement or movement is being attempted with spindle 11.

Persons wishing to practice the invention should remember that other embodiments and variations can be adapted to particular circumstances. Even though one point of view is necessarily chosen in describing and defining the invention, this should not inhibit broader or related embodiments going beyond the semantic orientation of this application but falling within the spirit of the invention. For example, those skilled in the art will appreciate that piezoelectric crystals with different shapes, different housings, clamping or mounting sleeves, seals, etc. can be used within the spirit of the invention and that the inventive electro micrometer can be adapted to many specific uses and circumstances.

I claim:

1. In a micrometer having a mounting sleeve and a movable spindle, the improvement comprising an electrically adjustable element arranged between said sleeve and a fixed mounting structure, said element comprising:

(a) a member fixed to said mounting structure;

(b) a piezoeelctric member having one region engaging said fixed member;

(c) means for securing another region of said piezo electric member in place relative to said sleeve;

(d) the dimension of said piezoelectric member between said regions being variable in the direction of relative motion of said spindle; and

(e) means for applying a voltage to said piezoelectric member for varying said dimension to adjust the distance between said sleeve and said mounting structure for fine adjustment of said micrometer.

2. The micrometer of claim 1 wherein said fixed member comprises a sleeve clamped to said mounting structure.

3. The micrometer of claim 2 wherein said fixed member surrounds said spindle.

4. The micometer of claim 3 wherein said piezoelectric member is generally tubular and coaxial with said fixed sleeve.

5. The micrometer of claim 4 wherein said piezoelectric member butts axially against a radial portion of said fixed member.

6. The micrometer of claim 5 wherein an O-ring is arranged between an axial portion of said fixed member and the inside of said piezoelectric member.

7. The micrometer of claim 1 wherein said securing means comprises a housing attached to and coaxial with said micrometer sleeve.

8. The micrometer of claim 7 wherein said piezoelectric member is generally tubular and coaxial with said housing.

9. The micrometer of claim 8 wherein one surface of said piezoelectric member is grounded, and a jack is arranged in said housing for an electrical conductor secured .4 to the other surface of said piezoelectric element to apply said voltage.

10. The micrometer of claim 9 wherein a grounding conductor is disposed between the inside surface of said piezoelectric member and said micrometer sleeve, and said electrical conductor is secured to the outside surface of said piezoelectric member.

11. The micrometer of claim 8 wherein said piezoelectric member butts axially against a radial portion of said housing.

12. The micrometer of claim 8 wherein said fixed member comprises a sleeve clamped to said mounting structure and surrounding said spindle.

13. The micrometer of claim 12 wherein said fixed member and said housing have mutually engaging and relatively movable surfaces.

14. The micrometer of claim 13 wherein an O-ring is disposed between said fixed member and said housing adjacent said mutually-engaging surfaces.

15. The micrometer of claim 12 wherein opposite ends of said piezoelectric member butt axially against said fixed member and said housing.

16. The micrometer of claim 15 including an O-ring arranged between an axial portion of said fixed member and the inside surface of said piezoelectric member.

17. The micrometer of claim 16 wherein a grounding conductor is arranged between said micrometer sleeve and the inside surface of said piezoelectric member and a jack is arranged in said housing for an electrical conductor secured to the outer surface of said piezoelectric member to apply said voltage.

18. The micrometer of claim 17 wherein said fixed member and said housing have mutually engaging and relative movable surfaces, and an O-ring is disposed between said fixed member and said housing adjacent said mutually-engaging surface.

References Cited UNITED STATES PATENTS 2,728,222 12/1955 Becker et a1. 73-105 3,108,469 10/1963 Dyer et a1. 7367.1 3,296,467 1/1967 Locher 3108.1 3,377,489 4/1968 Brisbane 310-83 OTHER REFERENCES Coherent Optics Inc., Model 44 Electromicrometer. Date: About November 1969 by applicantsadmission.

IBM Technical Disclosure Bulletin, Digital Micrometer, Vol. 3, N0. 11, April 1961.

WILLIAM D. MARTIN, JR., Primary Examiner US. Cl. X.R. 

